But of all the fresh considerations of Carson’s work, there’s one that stands out for me at the moment — a recent paper by two researchers of rhetoric and writing who dug in on “Silent Spring” drafts, notes and revisions and found that Carson had a remarkable and rare trait for someone so committed to raising public concern about a pressing environmental issue. Rather than downplay scientific uncertainty and gaps in understanding, she progressively amplified what was unclear about the human impacts of DDT and other synthetic compounds on humans and wildlife.

The authors, Kenny Walker, a doctoral candidate at the University of Arizona, and Lynda Walsh, an assistant professor of English at the University of Nevada, Reno, describe how surprised they were by this pattern, given a large body of work, including “Merchants of Doubt,” the book by Naomi Oreskes and Erik Conway, showing that inflating uncertainty has mainly been the task of industry-backed efforts to blunt public concern and policy.

With Carson’s approach to conveying risk, they write, she appears to have created “a bridge across the is–ought divide in science-related policy making, using the uncertainty topos to invite the public to participate by supplying fears and values that would warrant proposals for limiting pesticide use.”

This stands in stark contrast to the “Be Worried” approach that some have tried (in vain) on global warming over the years. Mind you, Carson’s book has plenty of passages, from beginning to end, warning powerfully of the “grim specter” of a poisoned future.

But this look inside Carson’s five-year writing process shows an approach to conveying risk that seems relatively rare in environmental messaging these days. [9:09 a.m. | Updated | William Souder offered an invaluable reflection on the paper after reading my post, which you can read in full below.]

Kenny Walker on Rachel Carson’s use of uncertainty to raise public concerns about DDT:

The 50th year anniversary of “Silent Spring” invites reflection not just on the book, but on how we have paid attention to it for half a century. We tend to celebrate “Silent Spring” from the moment of publication forward, and this tendency ignores the rich history before publication—the five-year long process of meticulous research, writing, and rewriting. We tend to forget that “Silent Spring” did not just arise from Rachel Carson’s head fully formed. It was part of an ongoing conversation about the uncertainties of life in the postwar period. If we focus on the process behind “Silent Spring,” and not just the product, what lessons might we learn about the strategies Carson used to enter the conversation and frame the scientific debate around toxic chemicals?

Brooks Studio, from the Rachel Carson Council.

In a study published last January, Dr. Lynda Walsh, an associate professor of English at the University of Nevada, Reno, and I sought to answer this question by researching Carson’s composing process, with a particular focus on the crucial topic of uncertainty. We defined uncertainty as both ignorance (we do not know) and risk (a probability distribution of likely outcomes), and identified 33 places in “Silent Spring” where Carson expressed uncertainty. I then went to the Carson Papers archive at the Beinecke Library at Yale University to examine her sources, and her drafting process at these 33 locations. What I found was that not only did Carson underline, circle, and annotate her sources with particular attention to uncertainty, she amplified its use in later drafts. Sitting there at the archives, I witnessed where and when Carson crossed out entire sections, and inserted expressions of ignorance and risk in order to frame her carefully selected case studies. In our paper we argued that Carson adapted and adopted uncertainty from her sources and deliberately used it to provide a site for public participation in scientific debates.

For example, chapter 3 is titled “Elixirs of Death.” In an early draft of one section, she tells us about the storage and accumulation of DDT in the human body, and how even small amounts have been shown to cause acute liver poisoning. She ends this section by telling us: “There has been no such parallel situation in medical history. We have some intimations as to what the ultimate consequences may be, but it is too early to know the full story.” Here she gives her readers some basic facts about DDT, and then claims ignorance: “[I]t is too early to know what will happen.” But the final version foregrounds uncertainty, ‘‘Scientists do not agree upon how much DDT can be stored in the human body,’’ and ends with a double dose of uncertainty as ignorance and risk: “All these facts . . . caused Food and Drug Administration scientists to declare as early as 1950 that it is ‘extremely likely the potential hazard of DDT had been underestimated.’ There has been no such parallel situation in medical history. No one yet knows what the ultimate consequences may be.”

These revisions are one example of a strategy we saw Carson use consistently: Add uncertainty at the level of ignorance to destabilize the science, then articulate the harms, hazards, or consequences behind our current actions, and drive it home with a visceral image of risk (which she does in this example through images of liver damage, the accumulation of DDT in milk and butter, and the ability of toxic chemicals to pass to breast-fed human infants, and to a fetus in utero). Other revisions from certainty to uncertainty show up in her direct quotes from soil scientists, and in a section about estrogen and uterine cancer. Only in her last draft does she add: “Although medical opinion is divided on the question, much evidence exists to support the view that similar effects may occur in human tissues.” These additions connect to her general thesis about ignorance and risk: “I do contend that we have put poisonous and biologically potent chemicals indiscriminately into the hands of persons largely or wholly ignorant of their potentials for harm.”

Carson’s choice to deliberately increase her use of uncertainty in “Silent Spring” came as a bit of surprise since in the well documented cases of tobacco, acid rain, and global warming, it was the skeptic’s strategy to amplify doubt, not the scientist’s. In Carson we saw a counter-example: her composing process suggested that uncertainty is a crucial site for public participation and precautionary action. Uncertainty’s ability to disrupt knowledge (“we don’t know”) and actualize risk (“potential for harm”) gave the public a place to draw their own inferences, make their own evaluations, assert their right to know the potential hazards they face, and to motivate policy action. Uncertainty provided the readers of “Silent Spring” a clearly defined role in an otherwise inaccessible scientific controversy. Uncertainty shaped the promise of Carson’s book: to let the public decide for themselves.

One of the primary lessons 50 years after the publication of “Silent Spring” is that expressing uncertainty is not just a skeptic’s position. Uncertainty is a way to manage scientific ethos and provide grounds for the public to participate in scientific controversies. Strategically managing uncertainty offers scientists a way to appear trustworthy, protect against bias, and assert their practical wisdom, moral virtue, and goodwill toward the audience. Scientists need to make it a habit to express uncertainty skillfully. They must do so in ways that provide an accurate assessment of choice in the face of our perpetual ignorance, and our inevitable uncertainties.

In a followup exchange after he sent his piece, Walker provided what I think is a valuable capping thought:

If you can be accurate yet still use uncertainty to frame the impact, you’re not only trustworthy, you’re interesting, and you effectively shape the terms of debate. We’ve all got to stop ignoring uncertainty, and instead learn to manage it. Fifty years later, I think that’s one of the primary lessons of “Silent Spring.”

9:09 a.m. Update

William Souder, the author of “On a Farther Shore,” sent this invaluable note this morning:

This is an illuminating and important study of “Silent Spring” and how Rachel Carson understood and deployed scientific uncertainty in making her arguments in the book…which turns 50 on this very day. And the conclusions reached by these authors make sense in light of Carson’s approach. A relentless reviser, Carson also depended in all of her books on a vast network of experts, scientists, scholars, and physicians who reviewed and commented on her work in progress. Carson listened to these reviewers.

This was particularly true in the section of “Silent Spring” dealing with cancer, which Carson re-wrote several times, in the process moderated her claims of a link between pesticides and the disease in part on the advice of her own oncologist (Carson was being treated for the breast cancer that eventually ended her life at 56).

I also think the authors of this study offer wise advice to those of us writing today about issues like climate change: Rather than cede the useful concept of uncertainty to those who would deny scientific consensus, we’d do better to embrace and explore uncertainty for what it is…a valuable and inevitable part of scientific discovery.

One more thing that makes this study of Carson’s approach so fascinating is that I think you have to try to imagine the context Carson was working in in the late 1950s/early 1960s. The idea of chemicals contaminating what Carson called “the total environment” was novel at the time. And it was her recognition of an exact parallel with the steady rain of fallout from nuclear testing that helped her explain what we knew…and didn’t know…about the consequences and potential collateral damage from heedless tampering with global ecosystems. It’s no accident that Baby Boomers became the vanguard of the environmental movement. They grew up drilling for Armageddon (“Duck and Cover”), and when they read Silent Spring they GOT IT.